Isolation and characterization of a cDNA clone showing C-myc binding-activity

A cDNA clone encoding a novel c-myc promoter binding protein (MBP-2) was isolated from a HeLa cell expression library. MBP-2 showed binding to the sequence from -46 to -64, relative to the P2 transcription start site of the human c-myc oncogene. This important regulatory sequence is necessary for optimal transcription from the P2 promoter of the c-myc oncogene. A single base substitution prevented binding of the recombinant MBP-2 to its target sequence. The MBP-2 cDNA hybridized to a 1.7 kb transcript from several human tissues. Mouse antisera to the recombinant MBP-2 showed binding to an approximately 80 kd protein from the HeLa and NIH3T3 cell lines by Western blot analysis. Nucleotide sequence analysis suggested that MBP-2 is a unique DNA binding protein and may play an important role in the regulation of c-myc transcription.